EP0127965A2

EP0127965A2 - A valve for regulating fluid flow

Info

Publication number: EP0127965A2
Application number: EP84303170A
Authority: EP
Inventors: Willard Edward Kemp
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-05-11
Filing date: 1984-05-10
Publication date: 1984-12-12
Also published as: CA1232893A; CA1216079A; GB8411936D0; EP0127965A3; US4588164A; NO841880L; GB2139739A; JPS59231272A; BR8402251A

Abstract

A through-conduit, double-wedging parallel seat gate valve has a monolithic semispherical body with a cylindrical flow passage and flange end connections. The body has a transverse chamber containing a rectangular gate movable across the passage between opened and closed positions. The chamber has an obround cross-section with parallel sides facing the sides of the gate and rounded ends facing the edges of the gate. Integral parallel guide surfaces on the body separate the rounded ends from the parallel sides, and these guide surfaces engage the edges of the gate. Replaceable seats aboutthe flow passage seal to the sides of the gate. Upper and lower closure members are releasably secured on annular sealing surfaces on the body and enclose the gate within the chamber. The flange and semispherical body can have the same radii as the bar stock from which the body is machined.

Description

THIS INVENTION relates to a valve for regulating fluid flows, and more particularly relates to a reciprocating gate valve.
The designs of valves have been improved continually for many years, and these designs are conformed to the type of flow control in which the valve is to be employed. One common commercial valve is the gate valve wherein a gate is moved reciprocally across a flow passage between open and closed positions.
The present invention concerns a gate valve with a reciprocating gate such as is used in high-pressure wellhead service. More particularly, the invention relates to a gate valve of the type having a gate with double sealing gate parts and parallel seats. The complementary gate parts have inclined plane devices which convert stem force to axial force for pressing the gate parts against the seats when the valve is adjusted into opened and closed positions.
There are many gate valves presently available for wellhead service. Examples of these gate valves are the (1) W-K-M "Pow-R-Seal", (2) Gulfco API Gate Vαlve, (3) Demco type N, (4) Vetco Manual Gate Valve, (5) Gray Gate Valve Model 5, and (6) Newco Gate Valves. All valves of this type have removable/replaceable seats, separate gate guide members to control gate reciprocation, and closures (bonnet and lower cap). As a result, the valve body and gate guide members are relatively complicated in manufacture and as a result, the gate valves are expensive.
In these gate valves of the through-conduit type, the gate assembly is always in contact with the seals to protect them from abrasion and corrosion, and also to keep the gale from vibration in fast fluid flows. When the valve is in the opened position, the flow passes through a hole in the gate. The hole is usually of the same size as the flow passage in the valve body. With the valve in its closed position, an imperforate part of the gate rests between the seals and effectively blocks fluid flow through the valve body.
Because of the service requirements on wellheads, these valves have large safety factors in their design. As a result, the valves are heavy. For example, a 350 bar model of 5 cm flow channel diameter (a 5000 psi model of 2 inch flow channel diameter) will weigh about 68 Kg (150 pounds) and a 5 cm (6 inch) model will weigh about 450 Kg (1000 pounds).
The valve bodies on prior gate valves for use on wellheads have in general been forged or cast so as to obtain large number production cost advantages. Further, the dimensions of the closures etc., were determined previously on the necessary strength criterion for the valve. Stated in a different way, the diameter of flanges on the valve bore no relationship to the sizes of the sealing surfaces on the closures, gate assemblies, etc.
According to this invention there is provided a through-conduit gate valve having a body containing a flow passage extending therethrough between end parts for connecting said valve into a piping system; a transverse chamber through said body extending across said flow passage; an elongated substantially rectangular gate movable through said chamber transversely across said flow passage between open and closed positions, said gate having in longitudinal space relationship an imperforate portion and a perforate portion with art opening conforming to said flow passage; gate guide means in said body for controlling transverse and lateral movement of said gate between open and closed positions; first and second closure members releasably secured on annular seal surfaces to said body for enclosing said chamber; one of said closure members receiving said imperforate portion of said gate when in its open position; wherein said body has a semispherical central portion containing said transverse chamber, said central portion having a radius less than or equal to "r" in a plane perpendicular to said flow passage; said transverse chamber has a symmetrical obround cross section defined by parallel sides facing the sides of said gate and rounded ends adjacent to the edges of said gate; and said first and second closure members are releasably secured along planes of detachment along annular sealing surfaces surrounding said transverse chamber on said body, said annular sealing surface each having a radius less than or equal to "rm" and extending parallel with said flow passage and transverse to gate movement within said transverse chamber, said plane of detachment of said closure member receiving said gate when in its open position being located substantially below the upper reaches of said gate when in its open position, said planes of detachment being spaced a distance "h" from the axis of said flow passage, the relationship of these radii and distance being
Preferably the distance "h" is about equal to the diameter "d" of said flow passage but not substantially greater than the value defined by the relationship
Conveniently said end parts for connecting with a piping system are pipe flanges with equal radii "rf" and the radii "rf" of said flanges are preferably substantially equal to the radius of said semispherical central portion of said body.
Advantageously the relationship between the several radii and said distance "h" is
Preferably said body is monolithic.
Conveniently said first and second closure members each carry a flat annular bearing surface of maximum radius "rb", said radius "rb" being - greater than the radius "rm", and preferably a plurality of threaded fasteners extend from each of said annular bearing surfaces through said first and second closure membes respectively, said threaded fasteners being integrally secured into said body within said annular sealing surfaces.
Preferably said annular sealing surfaces have a minimum radius "ri" and said transverse chamber and gate are enclosed within a cylindrical envelope prescribed by said minimum radius "ri".
Advantageously said first closure member includes a limited transverse chamber to accept a substantial movement of said gate thereinto between opened and closed positions thereof.
Preferably said first closure member carries a planar annular bearing surface at one end of said limited transverse chamber remote from said annular sealing surface thereon and above the reaches of said gate, and a plurality of threaded fasteners extend from said annular bearing surface through said first closure member and then integrally secure into said body within said annular sealing surfaces, the maximum radius of said annular bearing surface being greater than the radius "rm", but the inner edges of said exposed heads on said threaded fasteners extending inwardly over said cylindrical envelope prescribed by said maximum radius "ri".
In one embodiment the valve further comprises transverse grooves extending inwardly into said body from said transverse chamber and between said parallel sides and said rounded ends, said transverse grooves providing parallel strip guide surfaces for engaging the edges of said gate during its movement between opened and closed positions.
Preferably said transverse grooves are semicylindrical in cross-section and said strip guide surfaces are on the tangent at the intersection of said transverse grooves and said rounded ends of said transverse chamber.
In a preferred embodiment of a gate valve in accordance with the invention, the valve body can be machined easily and completely starting with bar stock having a diameter equal to that of the end connection flanges on the valve. The valve body of such an embodiment may have integral gate guides, and all annular sealing surfaces for the closures (bonnet and lower cap) may have maximum diameters of fixed relationship to the flanges. With this arrangement, the annular bearing surfaces on the body are less than the bolting bearing surfaces on the closures.
A preferred embodiment of the invention comprises a through-conduit, double-wedging, parallel-seat gate valve having a monolithic body containing a cylindrical flow passage extending between pipe flanges for connecting the valve into a piping system. A transverse chamber extends across the flow passage. A rectangular gate is mounted within the transverse chamber and arranged to be moved transversely across the flow passage between opened and closed positions. The transverse chamber has an oblong cross-section with parallel sides acting as gate guides to the sides of the gate and rounded ends facing the edges of the gate. Integral parallel strip guide surfaces on the body separates the rounded ends from the parallel sides. The strip guide surfaces engage as gate guides the edges of the gate. Replaceable annular seats are mouned in annular recesses formed within the parallel sides and about the flow passage. The seats engage in fluid tightness the sides of the gate. Upper and lower closure members are releasably secured to said body for receiving the gate in its movement between opened and closed positions.
In one preferred form, the valve body is machined from bar stock of a diameter equal in size to the pipe flanges. The closure members rest on annular sealing surfaces formed on the body having radii of fixed relationship to the flanges, and this body is semispherical with the same radius at its maximum diameter.
In another preferred form, the strip guide surfaces are provided by semicylindrical transverse grooves at the meeting between the parallel sides and rounded ends about the transverse chamber. More particularly, the strip guide surfaces are the tangents at the intersection of the grooves with the rounded ends.
It is to be noted that a preferred embodiment possesses the features that said body has unitary gate guide means and said transverse chamber has a symmetrical oblong cross-section defined by parallel sides facing the sides of said gate and rounded ends adjacent to the edges of said gate; and transverse grooves extend inwardly into said body from said transverse chamber and between said parallel sides and said rounded ends; and said transverse grooves within iaid rounded ends provide parallel strip guide surfaces for engaging the ecges of said gate during its movement between opened and closed positions.
The transverse grooves may be semicylindrical with said strip guide surfaces being on the tangent of said semicylindrical grooves intersecting with said rounded ends of said transverse chamber, and said transverse grooves may extend into said annular recesses mounting said annular seats whereby a tool, such as a screwdriver, can be used to pry said annular seats from said body. The annular recesses may be reduced diameter stepped surfaces such as stepped counterbores and said transverse grooves may extend only into the stepped surface of said annular recess immediately adjacent said transverse chamber. Said transverse chamber may have on obround cross-section and said semicylindrical grooves may have their centers substantially aligned in planes parallel with said sides of said transverse chamber and their centers also residing substantially at the meeting of said sides with said rounded ends whereby said strip guide surfaces are on the tangent of said semicylindrical grooves intersection with said rounded ends. The annular recesses may be reduced diameter stepped surfaces and said semicylindrical grooves extend only into the stepped surface of said annular recesses immediately adjacent said transverse chamber, and said annular seats have complementary reduced diameter surfaces to be received into said annular recesses.
ft-is also to be noted that a preferred embodiment of the invention comprises the features that a body with pipe flanges provides end parts for connection in a piping system, said body being formed solely from a length of bar stock having a radius "rs" substantially equal to the radii "rf" of said flanges, said flanges being formed at the ends of said bar stock and coaxially with the flow passage having a diameter "d", said body also having unitary gate guide means wherein said transverse chamber has a symmetrical obround cross-section defined by parallel sides facing the sides of said gate and rounded ends adjacent to the edges of said gate. There are transverse semicylindrical grooves extending inwardly into said body from said transverse chamber and between said parallel sides and rounded ends, the intersection of said semicylindrical grooves with said rounded ends on a tangent providing strip guide surfaces for engaging the edges of said gate during its movement between opened and closed positions, stepped counterbores provide annular recesses about said flow passages in said parallel sides, there are annular seats removably mounted within said counterbores, and said semicylindrical grooves extend into said stepped counterbores immediately adjacent to said transverse chamber whereby a tool can be inserted within said grooves to pry said annular seats from said counterbores and to displace said annular seats into said transverse chamber.
It is also to be noted that the preferred embodiment of the invention possesses the features that the transverse chamber has in said body an obround cross-section with parallel sides facing in close proximity the sides of said gate and rounded ends adjacent to the edges of said gate; and parallel strip guide surfaces are provided transversely to said flow passage directly on said body for engaging the edges of said gate, and said strip guide surfaces separate said rounded ends from said parallel sides.
In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure I A is a partial side elevation of a gate valve in accordance with this invention;
Figure IB is a partial vertical section of the gate valve of Figure IA;
Figure 2A is a partial vertical section taken along line 2A-2A of the valve in Figure I A;
Figure 2B is a vertical section taken along line 2B-2B of the valve in Figure I B;
Figure 3 is a cross-section taken along line 3-3 of the valve in Figures . IA-IB; and
Figure 4 is a vertical section taken along line 4-4 of the valve in Figure IB.

Referring to the drawings, and particularly to Figures IA and IB, and 2A and 2B, there is shown a reciprocating gate valve in accordance with this invention. The valve I has a body 12 with a cylindrical flow passage 13 extending therethrough between end parts for connection into a piping system. These end parts may be API flanges 14 and 16 carrying the usual holes 15 to accept bolts etc., for piping connections. The flanges have equal radii "rf".
The body 12 carries a bonnet or upper closure 17 which houses the usual stem 18 that can be rotated by an external handwheel 19. The stem extends through the tubular closure 17, and is mounted within bearings 21 and fluid tight chevron packings 22. A Zerk fitting 23 allows greasing of the bearings 21. A pressure fitting 24 allows injections of a lubricant/sealant into the packing 22.
The lower part of the closure 17 carries a limited transverse chamber 26 into which is received the upper portion of a gate assembly 27 when the valve 1 is in its opened position. More particularly, the gate assembly is reciprocably mounted upon the threaded end 28 of the stem 18 by its threaded engagement of said end 18 within the nut 29 carried by the gate assembly.
The gate assembly 27 is composed of complementary gate discs or parts 31 and 32 that engage upon inclined plane surfaces 33 and 34. A loading spring (not shown) maintains these gate parts in tight engagement. As a result, these inclined plane surfaces force the gate parts laterally apart against fluid seats when the gate assembly is in its opened or closed positions. The gate parts 31 and 32 are imperforate in their upper extremity while their lower portion carries a round opening 36 aligning with, and of the same diameter "d" as the flow passage 13. A pressure fitting 37 may be provided on the closure 17 for injecting lubricant/sealant into the gate assembly 27.
The body 12 carries a cap or tubular lower closure 38 which has a limited transverse chamber 39 in which the gate assembly is received when the valve is in the closed position. The upper and lower closures are secured by suitable bolt openings 40 and 45 to the body 12 by cap bolts 41 and 42, respectively. Also, fluid tight connections between the closures and the body are provided by metal seal rings 43 and 44 resting in the usual seal grooves in the mating parts.
More particularly, the upper closure 17 seats upon a planar or flat annular sealing surface 46 provided upon the body 12. The surface 46 has a maximum radius "rm". In addition, the surface 46 rests in a plane parallel to the axis 47 of the flow passage 13, but spaced therefrom by a distance "h". The lower closure 38 similarly seats upon a planar or flat annular sealing surface 48 provided on the body 12. The surface 48 can also be parallel with and spaced from the axis 47 by a distance "h".
The cap bolts 41 abut a planar or flat bearing surface 49 which has a maximum radius "rb". This surface resides in a plane parallel to sealing surface 46, but it is spaced above the upper end 51 of the chamber 26. As a result, the cap bolts 41 transverse the closure 17 and threadedly secure into threaded openings 53 within the sealing surface 46. The portion 52 of the upper closure 17 traversed by the cap bolts 41 can be cylindrical in external configuration. Preferably, the open end of the portion 52 has a circumferential rim 54 that overhangs the sealing surface 47. The rim 54 may provide a receptical for grease, etc. to exclude debris, water or other corrodant and also it assists in alignment of the closure 17 onto the body 12.
The lower cover 38 may also carry a similar rim 56. The cylindrical portions 52 and 38 with their rims 54 and 56 provide smooth external surfaces transition to the body 12.
The body 12 can be manufactured from forgings or castings, but it also can be manufactured efficiently from bar stock of a suitable metal, such as wrought iorn or stainless steel. For this purpose, a length of cylindrical bar stock is used of an adequate length and of a radius "r".
Preferably, the radius "r" is substantially equal to the radius "rf" of the flanges 14 and 16. The bar stock is axially bored to produce the flow passage 13. Now, the flanges 14 and 16 are machined onto the bar stock.
The central portion 57 of the body 12 about the gate assembly 27 is turned into a semispherical shape having a maximum radius "r" in a plane perpendicular to the axis 47 of the flow passage 13 (best seen in Figure 3).
The intermediate body portions 58 and 59 are now turned cylindrically
between the central body portion 57 and the flanges 14 and 16.
Preferably, the body 12 has a relationship wherein the flanges 14 and 16, semispherical body portion 57 and the annular sealing surfaces 46 and 48 have radii of a fixed relationship. For this result, the annular sealing surfaces 46 and 48 are cut onto the body forming parallel planes of detachment, which planes are perpendicular to the axis of gate movement and also parallel to the axis 47 at a distance "h" therefrom. Stated in another manner, these sealing surfaces in their maximum radii "rm" are equal in diameter to a circle formed by truncating the semispherical body portion 57 at the distance "h" from the axis 47.
More particularly, the relationship above stated conforms to the formular r²= (rm)² + (h)² when r is the maximum radius of the spherical body portion 57.
Also, the relationship in the body 12 relative to the flow axis 47 conforms to the formula
Additionally, the relationship in the body 12 relative to the flange radii conforms to the formula
With the valve 11 constructed in accordance to the above relationships, the maximum strength from a machined bar stock is produced while the valve means remains very compact in the body 12.
As shown, the truncation of the body 12 leaves only a small curve 60 from the semispherical portion 57 exposed below the closures. However, the larger the valve diameter, the greater the curve 60 from the semispherical portion exposed below the closures as seen in Figure 4.
Also, the annular bearing surface 49 has a maximum radius "rb" at the cap bolts that is greater than the maximum radius "rm" of the annular seating surface 46. Thus, the cap bolts are arranged in a circle less than the radii "rb" and "rm". This arrangement permits a very compact arrangement of the closure 17, and also, if desired, of the closure 38.
As mentioned, the gate assembly 26 cooperates with seals for fluid tight conditions at the opened and closed positions of the valve 11. For this purpose, as best seen in Figure 3, stepped counterbores or annular recesses 61 and 62 are formed within the body 12 about the flow passage. Annular seals 63 and 64 are securely mounted within these recesses 61 and 62, respectively. These seals have reduced diameter stepped portions engaging fluid tightly within the recesses. The enlarged diameter portions of the seals have flat faces 66 and 67 parallel to the sides of the gate ports 31 and 32 and include resilient sealing rings 68 to produce the fluid tight seal to the gate assembly. The flat faces of the seals provide gate guide surfaces to the sides 69 and 7 of the gate parts 31 and 32. As in the usual gate valve, these seals 63 and 64 can be removed and replaced as necessary for proper valve operation.
The gate assembly 27 is contained within a transverse chamber 72 within the body 12. The chamber 72 has a uniform oblong cross-section taken transversely to the axis of gate movement in the body 12. Preferably, the chamber 72 has an obround cross-section formed in the body 12 with the parallel sides 70 and 75 facing the sides 69 and 71 of the gate assembly 27. The parallel sides 70 and 75 will act as gate guides. Also, the chamber 72 has equal radii rounded ends 73 and 74 facing the edges 76 and 77, respectively, of the gate assembly 27.
In addition, the body 12 integrally carries parallel strip guide surfaces 78,79, 81 and 82 for engaging the edges 76 and 77 of the gate assembly 27. Thus, the gate assembly is guided axially, and confined laterally by the faces 66 and 67 of the seals and the strip guide surfaces 78, 79, 81 and 82. Since these strip guide surfaces are integral with the body 12, the body is much more compact about the chamber 72 than conventional gate valves having separate gate guide shoes or members.
Preferably, the strip guide surfaces are provided by transverse parallel grooves 83, 84, 86 and 87 which extend inwardly into the body 12. These grooves are positioned between the parallel sides 70 and 75, and the rounded ends 73 and 74. These grooves extend in the body 12 along the parallel sides 70 and 75 and preferably intersect the counterbore enlarged diameter recesses 61 and 62, immediately adjacent the chamber 72. As a result, the large diameter portion of the seals 63 and 64 are exposed at the grooves. With the gate assembly 27 removed from the body 12, a screw driver or other tool inserted into these grooves can be used to pry the seals from the counterbored recesses formed into the parallel sides 70 and 75. Replacement seats are reinserted into these recesses and driven firmly into the recesses 61 and 62 from the chamber 72.
The grooves 83, 84, 86 and 87 are preferably semicylindrical in cross-section with their loci positioned in planes aligned with the faces 66 and 67 of the seals (and slightly inwardly of the parallel sides 70 and 75). Also, the loci of these semicylindrical grooves are placed at about the meeting of the parallel sides 70 and 75 with the rounded ends 73 and 74. These semicylindrical grooves have radii such that the strip guide surfaces 78, 79, 81 and 82 are on the tangent of the intersection of the grooves with the rounded ends.
The chamber 72 and grooves 83, 84, 86 and 87 are readily machined into the body 12, especially when formed from the bar stock. After the annular sealing surface 46 and 48 have been cut, round holes can be bored into the body 12 at the locus of the semicylindrical grooves and they extend between the annular sealing surfaces. How, a cylindrical milling cutter with a diameter slightly less than the distance between the parallel sides 70 and 75 is employed to cut out of the body the chamber 72 with its parallel sides and rounded ends. As a result, the round holes become after milling the semicylindrical grooves between the parallel sides and the rounded ends with the tangents at their intersection being the parallel strip guide surfaces 78, 79, 81 and 82. Not only are these strip guide surfaces integral with the body 12, but they are formed simultaneously with cutting of the chamber 72. The parallel sides 70 and 75 can now be counterbored to produce recesses 61 and 62.
As best seen in Figure 3, the annular sealing surfaces 46 and 48 have a minimum radius "ri" and enclose the chamber 72, the semicylindrical grooves and the gate assembly 27. More particularly, no portion of the gate assembly and chamber 72 not concentric with the passage 13 extend laterally outside of a cylindrical envelope prescribed by this minimum radius "ri". Thus, the valve body 12 is extremely compact, yet strong but economically machined from bar stock.
The exterior surface of the bdy 12 can be machined into the flanges, the semispherical portion 57 and the cylindrical body portion 58. As seen in Figures 2B, 3 and 4, the radii of the body decrease as a function with the distance from the portion 57 towards the portions 58. As the size of the valve increases, so does the radius "r" of the body 12. In addition, the curves 60 merge smoothly into the annular sealing surfaces 46 and 48.
A pressure fitting 88 on the closure 38 allows injection of lubricant into chamber 39.
From the foregoing, it will be apparent that there has been provided a novel reciprocating gate valve for controlling fluid flows, especially at wellheads, that is compact, easily machined from bar stock and has integral gate guides but yet is as strong and serviceably as conventional gate valves employing body castings. It will be appreciated that certain changes and alterations in the present gate valve can be made without departing from the spirit of this invention.

Claims

1. A through-conduit gate valve (11) having a body (12) containing a flow passage (13) extending therethrough between end parts (14, 16) for connecting said valve into a piping system; a transverse chamber (72) through said body extending across said flow passage; an elongated substantially rectangular gate (27) movable through said chamber transversely across said flow passage between open and closed positions, said gate having in longitudinal space relationship an imperforate portion and a perforate portion with an opening (36) conforming to said flow passage; gate guide means (78-82) in said body for controlling transverse and lateral movement of said gate between open and closed positions; first and second closure members (17, 38) releasably secured on annular seal surfaces (46) to said body for enclosing said chamber; one of said closure members receiving said imperforate portion of said gate when in its open position; characterised in that said body has a semispherical central portion (57) containing said transverse chamber, said central portion having a radius less than or equal to "r" in a plane perpendicular to said flow passage; and in that said transverse chamber has a symmetrical obround cross section defined by parallel sides (70, 75) facing the sides (69, 71) of said gate and rounded ends (73, 74) adjacent to the edges of said gate; and in that said first and second closure members are releasably secured along planes of detachment along annular seating surfaces surrounding said transverse chamber on said body, said annutar sealing surface each having a radius less than or equal to "rm" and extending parallel with said flow passage and transverse to gate movement within said transverse chamber, said plane of detachment of said closure member receiving said gate when in its open position being located substantially below the upper reaches of said gate when in its open position, said planes of detachment being spaced a distance "h" from the axis of said flow passage, the relationship of these radii and distance being

2. A valve according to claim 1, wherein the distance "h" is about equal to the diameter "d" of said flow passage but not substantially greater than the value defined by the relationship

3. A gate valve according to claim I or claim 2, wherein said end parts for connecting with a piping system are pipe flanges with equal radii "rf" and the radii "rf" of said flanges are substantially equal to the radius of said semispherical central portion of said body.

4. A gate valve according to claim 3, wherein the relationship between the several radii and said distance "^h" is (rf) ⁼ (^rm)^{2 +} (_h)2.

5. A gate valve according to any one of the preceding claims, wherein said body is monolithic.

6. A gate valve according to any one of the preceding claims, wherein the first and second closure members each carry a flat annular bearing surface (49) of maximum radius "rb", said radius "rb" being greater than the radius "rm", and wherein a plurality of threaded fasteners (41,42) extend from each of said annular bearing surfaces through said first and second closure members respectively, said threaded fasteners being integrally secured into said body within said annular sealing surfaces.

7. A gate valve according to any one of claims to 5, wherein said annular sealing surfaces have a minimum radius "ri" and said transverse chamber and gate are enclosed within a cylindrical envelope prescribed by said minimum radius "ri".

8. A gate valve according to claim 7, wherein said first closure member includes a limited transverse chamber (26) to accept a substantial movement of said gate thereinto between opened and closed postions thereof.

9. A gate valve according to claim 7 or 8, wherein said first closure member carries a planar annular bearing surface (49) at one end of said limited transverse chamber remote from said annular sealing surface thereon and above the reaches of said gate, and a plurality of threaded fasteners (41) extend from said annular bearing surface through said first closure member and then integrally secure into said body within said annular sealing surfaces the maximum radius of said annular bearing surface being greater than the radius "rm", but the inner edges of said exposed heads on said threaded fasteners extending inwardly over said cylindrical envelope prescribed by said maximum radius "ri".

10. A gate valve according to any one of the preceding claims, further comprising transverse grooves (83, 84, 86, 87) extending inwardly into said body from said transverse chamber and between said parallel sides and said rounded ends, said transverse grooves providing parallel strip guide surfaces for engaging the edges of said gate during its movement between opened and closed positions.

11. A gate valve according to claim 10, wherein said transverse grooves are semicylindrical in cross-section and said strip guide surfaces are on the tangent at the intersection of said transverse grooves and said rounded ends of said transverse chamber.